1. Field of the Invention
This invention relates to a method of manufacturing a grafted resin composition, which is useful as an adhesive, coating agent, quality improver, microdispersion promoter, polymer alloy precursor, functional molding material, agent for providing solubility of polymer, etc. and permits a high grafting efficiency to be obtained.
2. Prior Art
Heretofore, ethylene polymers have been used extensively owing to their excellent characters, and also there have been attempts to improve their characters and use them in new fields.
For example, low density ethylene polymers have been used as molding materials because the their moldability and the satisfactory physical and chemical properties of products made therefrom.
Also, it has been practiced to mix vinyl polymers, e.g., polystyrene, with low density ethylene polymers as a molding material, in order to improve the rigidity, dimensional stability, printing property, etc. of the low density ethylene polymers.
Further, it is well known in the art that epoxy-group-containing olefin copolymers provide satisfactory adhesive force as an adhesive to bond together metal and plastic materials due to their polarity. Further, since they have elasticity and reactive properties, they are used as condensation series polymers; particularly, they are used as impact improving agents by being reacted with engineering plastics.
Further, since the ethylene-(meth) acrylic ester copolymers and .alpha.-olefin-vinyl ester copolymers have excellent flexibility, weather-proof property and impact resistance, they are extensively used as molding materials and .alpha.-olefin-vinyl ester copolymers are also broadly used for hot-melt adhesives. Further, recently there have been attempts as both copolymers to use impact resistance improving agents for engineering plastics.
Further, since ethylene-propylene copolymer rubber and ethylene-propylene-diene copolymer rubber have excellent rubber elasticity, flexibility, coldness-proof property and weather-proof property, they are extensively used as rubber materials, and also recently there have been attempts to use them as impact resistance improving agents for engineering plastics.
However, since olefin polymers and vinyl polymers are not satisfactorily compatible with each other, it is not practiced to incorporate more than 10% by weight of vinyl copolymer in mixtures of them. Usually, the vinyl polymer is incorporated in an amount of only by 0.2 by 5% by weight. Even when such a small quantity of vinyl copolymer is mixed, the impact resistance of the mixtures is reduced due to the unsatisfactory mutual solubility of the two resins, and also a deteriorated appearance is apt to occur.
Further, when ethylene copolymers are used as impact resistance improving agents, sufficient impact resistance improvement effect can not be obtained because of the low mutual solubility and dispersion property.
For example, in the case of the epoxy-group-containing olefin copolymer, the scope of applications is limited to materials which can react with an epoxy group. Therefore, it has been apt to occur that sufficient adhesive force can not be obtained with materials which do not react with an epoxy group, e.g., vinyl copolymers, or sufficient impact resistance can not be obtained due to low dispersion force with respect to materials.
Therefore, there have been attempts to increase their compatibility with engineering plastics.
For example, there have been attempts to increase the compatibility with the engineering plastics by increasing the proportion of ethylene-(meth) acrylic ester copolymer component and .alpha.-olefin-vinyl ester copolymer component with respect to the (meth) acrylic ester or vinyl ester. Further, it has been attempted to introduce functional groups such as epoxy group, carboxyl group and acid anhydride group for reaction with residual functional groups of engineering plastics, particularly, condensation engineering plastics, to increase the compatibility and improve the impact resistance improvement effect. In the meantime, it is well-known in the art that graft copolymers, in which a polymer having a high compatibility with other resins and a functional polymer are chemically combined in a molecule, are preferred to improve the compatibility with respect to other resins.
Generally, as a method of grafting combining a vinyl polymer with an olefin polymer, there has been proposed an olefin polymer, which is obtained by graft polymerizing a vinyl monomer, e.g., styrene monomer, with olefin polymer by irradiation with ionizable radiation. This method provides considerable effects for causing uniform dispersion of the vinyl copolymer in the olefin polymer. As further well-known method, there is a liquid graft polymerization method making use of such a solvent as xylene or toluene. Also, there is an emulsification graft polymerization method.
Further, it has been proposed to impregnate olefin polymer particles with vinyl monomers and cause polymerization of the resultant system using an aqueous suspension (as disclosed in Japanese Patent Publication No. Sho 58-51010 Japanese Patent Publication No. Sho 58-53003. According to this method, in the polymerized resin composition, the vinyl polymer is uniformly mixed. With this method, satisfactory results can be obtained in comparison to other methods.
However, the prior art method for causing graft coupling of vinyl polymers of olefin polymers is not fully satisfactory. More specifically, the method of irradiation by ionizable radiant rays is based on a special process of a radiation graft polymerization process. Therefore, this method has problems in economy and encounters difficulties in putting it into practice. Further, in this method there is a limitation in the amount of vinyl monomers to be introduced.
Further, in the solution graft polymerization process, polymerization is done in a state in which the system to be graft polymerized is diluted in a large quantity of solvent. From the standpoint of the compatibility of the olefin polymer, there is less opportunity for contact with vinyl monmers, polymerization initiators, and olefin polymers with one another, and generally the reaction efficiency of the vinyl monomers is low. Further, there are complicated after-treatment steps for vinyl monomers, which is economically disadvantageous.
Further, there is the emulsification graft polymerization process. In this case, the reaction is limited only to the on-surface reactions of olefin polymer particles. In the process of polymerization in a water suspension, the grafting efficiency of the resin composition obtained by this process is low. Therefore, vinyl polymer particles which have been uniformly dispersed at the end of the completion of polymerization, are liable to be agglomerated secondarily due to heating in the secondary processing or contact with the solvent, thus giving rise to problems when using the obtained resin composition as microdispersion promoters, compatibilizers of polymer alloys and agents for providing polymer compatibility.